The Science Of Getting Rich by Wallace D. Wattles is a timeless classic written many years ago. Over a century ago, in fact.
But it's a practical, step-by-step guide whose thought-provoking principles and strategies, though they were written in 1910, are still very much applicable to this day. And probably more so.
I'm a firm believer in the idiom that you are what you think. And this book drives that point home. So I highly recommend that your read this book. Below is a direct link to the version on the Gutenberg Public Domain Library.
“The men and women who practice the foregoing instructions will certainly get rich, and the riches they receive will be in exact proportion to the definiteness of their vision, the fixity of their purpose, the steadiness of their faith, and the depth of their gratitude.”
— Wallace D. Wattles